Finding the difference between 2 dates in PHP - php

Question

I am using PHP, jQuery AJAX and HTML to create a timesheet system, for this the user needs to select 2 dates within 1 month of each other. The system as yet is working and shows (very limited) data.
BUT! When I actually select a date over the month limit (i.e. 2 months further than the start or another year after the start), it still shows the table with the data.
For this I have this check:
$dt1 = new DateTime($_REQUEST['startdate']);
$dt2 = new DateTime($_REQUEST['enddate']);
$diff = date_diff($dt1, $dt2);
// I have tried this the other way around and get the same result...
if($diff->m > 1 || $diff->y > 1)
{
print("<center><strong>Time between dates it too great<br />Please choose another date or time within a month of each other</strong></center>");
die();
}
The dates are passed by a jQuery datepicker object via AJAX, and the dates I use, for example, are passed as such:
11/14/2015 (start date) && 12/14/2015 (end date) - should show data
09/14/2015 (start date) && 12/14/2015 (end date) - should not show data but does
11/14/2015 (start date) && 12/14/2016 (end date) - should not show data but does
There is a check in place that sees if the dates given start before the other and this works, I have tried the same kind of thing for this check, but without success, this check is as such:
function CountDaysBetween($startDate, $endDate)
{
$begin = strtotime($startDate);
$end = strtotime($endDate);
if ($begin > $end) {
echo "start date is in the future! <br />";
return;
} else {
$no_days = 0;
$weekends = 0;
while ($begin <= $end) {
$no_days++; // no of days in the given interval
$what_day = date("N", $begin);
if ($what_day > 5) { // 6 and 7 are weekend days
$weekends++;
};
$begin += 86400; // +1 day
};
$working_days = $no_days - $weekends;
return $working_days + 1;
}
}
Edit
Dates 2 or more months apart within the same year work, tested again and this is the case, but dates into the next year do not

Answer 1

In your first part of the php code, you have put this operator>, but the problem is it means, everything Smaller than 1, not everything that is smaller than one or equal to 1. The easy solution is to change the operators to >=; which means everything that is equal to 1 or smaller than 1.

Answer 2

The date_diff constructs in PHP suck monkeyballs. Far more practical is to use straight comparisons instead:
$dt1 = new \DateTime($_REQUEST['startdate']);
$dt2 = new \DateTime($_REQUEST['enddate']);
$dt1->add(new \DateInterval('P1M'));
echo ($dt1 < $dt2 ? 'Less' : 'More') . ' than a month';
Also please do not use $_REQUEST, it has potentially terrible security issues. You should use $_GET, $_POST or $_COOKIE according to what you explicitly expect.